1. Field of the Invention
The present invention relates to improvements in folding tent frames for foldable or collapsible tents used as a protection against the rain or sun or the like.
2. Description of the Related Art
Folding tent frames are disclosed, for example, in Japanese Pat. Nos. 2597670, 2625255, 2836956, 2949648; unexamined Japanese patent application No. 1-142183, unexamined PCT patent application (published in Japan) 10-503249; registered utility model Nos. 3057222, 3057223; U.S. Pat. Nos. 4,607,656; 4,641,676; 4,779,635; 4,885,891; 4,947,884; 5,244,001; 5,275,188; 5,421,356.
These folding tent frames are essentially made up of telescopic expandable sets of poles, each set having at least two polesxe2x80x94a lower pole and an upper polexe2x80x94the lower pole smaller than the upper pole in diameter; fixed couplers put at the top of the upper poles; movable couplers put on the upper poles at a position lower than the fixed couplers; and traverse frame members joined in a foldable scissor manner to the fixed couplers and the movable couplers.
In these folding tent frames, the upper pole is usually larger in diameter and the movable coupler can slide along the upper pole alone. This simplifies the construction of the folding tent frame.
However, the problem with these prior art frames is that while the construction is simple, these frames are poor in strength and stability because the lower pole is smaller in diameter.
In view of the disadvantages of the prior art, it is an object of the present invention to provide a folding tent frame with improved strength and stability.
The folding tent frame according to the present invention essentially comprises telescopically expandable sets of poles, each set having at least two polesxe2x80x94an upper pole and a lower polexe2x80x94the upper pole is smaller than the lower pole in diameter; fixed couplers are disposed at the top of the upper poles; stoppers put on the upper pole at a position lower than the fixed couplers that prevent at least the lowest poles from moving up and can be juxtaposed and continuous with the lowest pole; movable couplers are slidably disposed on the stopper and the lower pole and kept by the stopper from moving up; and traverse frame members joined to a fixed coupler and a movable coupler in a foldable, scissor manner.
To set up the folding-type or collapsible tent frame, the movable coupler is fit over the stopper that limits upward movement of the movable coupler and the upper pole is pulled out from the lower pole.
When the folding-type or collapsible tent frame is folded, the upper pole is withdrawn into the lower pole and at least the lower pole is kept by the stopper from moving up. The lower pole is juxtaposed and continuous with the stopper so that the movable coupler is slid from the stopper down the lower pole. At this point, the lower pole and the stopper come into contact and are continuous with each other, permitting the movable coupler to slide smoothly between them.
It is noted that since the lower pole is larger than the upper pole in diameter, the upright pole set is high in buckling strength and improved in stability, too.
In a preferred embodiment, the upright pole set is formed of two polesxe2x80x94an upper pole and a lower pole. This makes it possible to build an expandable upright pole set with the least number of poles.
In another preferred embodiment, the upright pole set is formed of three polesxe2x80x94an upper pole, a middle pole and a lower pole. This makes it possible to build an expandable upright pole set with a low number of polesxe2x80x94an upright pole set that is long in extended length and short in withdrawn length.
The traverse frame member is preferably square in cross section. This construction evenly distributes the load from above or from the side, thus reducing the twisting of the whole folding tent frame and reducing the weight of the tent frame itself.
It is desirable that the second lowest pole (i.e., the middle pole in a three-pole embodiment or the upper pole in a two-pole embodiment) be provided with a wheel that projects from the lowest pole and comes in contact with the ground when the poles are withdrawn. The wheel facilitates moving the folding tent frame when the poles are withdrawn. When the poles are extended, the wheel withdraws from the bottom pole. The bottom pole can be securely grounded.
It is desirable to provide a movable coupler fastening means between the stopper and the movable couplerxe2x80x94means to fasten the movable coupler to the stopper. That can prevent the movable coupler from moving down inadvertently.
It is also desirable to provide an extended pole fastening means to keep the upright pole set in an extended state. This can prevent the upright pole set from contracting inadvertently.
It is desirable to provide a withdrawn pole fastening means between the poles that keeps the withdrawn poles fixed and an elastic body to push up the upper pole out of the lower pole. According to this arrangement, when the withdrawn pole fastening means is disengaged, the upper pole can extend from the lower pole by the elastic body, a spring, for example. That lightens the labor of expanding the poles in setting up the folding frame.
It is desirable that the traverse frame member be integrally provided with washers at the end of the traverse frame member. This saves the trouble of inserting a washer every time the frame is set up, and facilitates setting up.
It is desirable that the movable coupler fastening means includes an engaging hole on the pole; a latch provided on the movable coupler that can be put into the engaging hole; a spring to bias the latch toward the engaging hole; and holding means for keeping the latch in a disengaged position. In this arrangement, the latch can be kept in a disengaged position by the holding means, and this makes it easy to move the movable coupler up or down.
It is further desirable that the movable coupler fastening means includes an engaging hole on the pole; a latch provided on the movable coupler that can be put into the engaging hole; a spring to bias the latch toward the engaging hole; and an inclined surface provided on the latch, wherein the inclined surface moves the latch to the disengaging position as it comes in contact with the lower pole. According to this arrangement, it is possible to hold the latch in a disengaged position by utilizing the contracting movement of the lower pole. That is, with no special procedures, the movable coupler can be raised.
Further objects, features and advantages of the present invention will become apparent from the Detailed Description of Preferred Embodiments, which follows, when read along with the attached Drawings.